doc: fix indentation on http2 doc entry

PR-URL: https://github.com/nodejs/node/pull/36869
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Pooja D P <Pooja.D.P@ibm.com>
Reviewed-By: Harshitha K P <harshitha014@gmail.com>
Reviewed-By: Daijiro Wachi <daijiro.wachi@gmail.com>

doc/api/http2.md

@@ -1769,7 +1769,7 @@ the request body.
 When this event is emitted and handled, the [`'request'`][] event will
 not be emitted.
 
-### Event: `'connection'`
+#### Event: `'connection'`
 <!-- YAML
 added: v8.4.0
 -->
@@ -1957,7 +1957,7 @@ the request body.
 When this event is emitted and handled, the [`'request'`][] event will
 not be emitted.
 
-### Event: `'connection'`
+#### Event: `'connection'`
 <!-- YAML
 added: v8.4.0
 -->